Shell command completion is provided by the script at /misc/completion/ipfs-completion.bash.
The simplest way to see it working is to run
source misc/completion/ipfs-completion.bash
straight from your shell. This
is only temporary and to fully enable it, you'll have to follow one of the steps
below.
For bash, completion can be enabled in a couple of ways. One is to copy the
completion script to the directory ~/.ipfs/
and then in the file
~/.bash_completion
add
source ~/.ipfs/ipfs-completion.bash
It will automatically be loaded the next time bash is loaded.
To enable ipfs command completion globally on your system you may also
copy the completion script to /etc/bash_completion.d/
.